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Fine bubbles, including microbubbles and ultrafine bubbles (UFBs, often referred to as nanobubbles), have attracted increasing attention for a wide range of environmental and engineering applications. In this presentation, I will introduce our recent studies on the characterization and environmental applications of UFBs, with particular emphasis on their electrical properties. The surface charge, zeta potential, and electrical conductivity of UFB dispersions will be discussed in relation to bubble generation conditions, the surrounding ionic environment, and bubble stability. I will also present examples of how these physicochemical characteristics are related to the behavior and performance of fine bubbles in environmental processes.
Another important issue is the reliability and comparability of fine-bubble measurements. Different measurement principles and experimental conditions can lead to significant variations in the measured bubble size and number concentration, particularly for UFBs. I will therefore introduce current international activities toward the standardization of fine-bubble characterization and evaluation methods, including recent developments within ISO/TC 281.
Through these studies, I will discuss how a better understanding of the electrical and interfacial properties of fine bubbles, together with the establishment of reliable measurement methods and standardization frameworks, can contribute to both fundamental fine-bubble science and the development of practical environmental technologies.